Jesus left the Apostles in charge of his Church. He told them to go and teach, not write a book. Yes, the Bible is the word of God, but neither Jesus nor the Bible tell us that the Bible was to be our sole authority once the Apostles, the original Church leaders, had finished writing it. Even Paul tells us to continue believing both what he wrote to the congregations, and what he taught verbally. A bit pointless if all he taught had been put into the texts they had.
Rejecting the Church, and going on their own to read the Bible and interpret it for themselves, Protestantism has resulted in 37000 denominations – mid 2005. While the number is debatable, and 37000 is obtained by counting individual congregations not united under a higher body, the fracturing of Christianity is obvious.